Conventionally, there is known a disposable diaper which is provided with a fastening tape. For example, Japanese Laid-Open Patent Publication No. 2004-538089 (Patent Literature 1) discloses a disposable diaper in which a fastening tape having an attachment is folded into a Z shape so that the attachment is detachably joined to a diaper main body. In the Patent Literature 1, the fastening tape is folded for temporarily joining the attachment to the diaper main body, prior to use of the disposable diaper.